I saw Ewan playing in a guitar duo called Mystery Pacific a few years ago at the Bay of Islands Jazz festival and he was fantastic. I felt like such a faker there playing gigs in the company of talented musicians like him. They were certainly full of the spirit of gypsy jazz and swing and were a pleasure to listen to, and also extremely personable to talk with. Pity the festival has no interest (money?) in bringing them back again as I'm starved for some good Manouche jazz up here lately.
I think what Nick was alluding to regarding the differences between the oval and D holes is that the original Selmer designs were made by an Italian man named Mario Maccaferri and built in conjunction with the Selmer factory in France. Mario pioneered a number of the innovations in it's construction, including borrowing the idea of the pliage (or bent top) from mandolin building, and laminating the back and sides for strength and stability. They evolved the design over the course of a number of years and varied from 4 to 6 strings, flat/slotted headstocks,variations of scale length, nylon and steel strings, D-hole and oval hole shaped soundholes etc. They settled on a few steel string models including a shorter-scale length with a D-hole (grande bouche), favoured by rhythm guitarists and a longer scale length with an oval hole (petite bouche) used by the lead players and popularised by Django. These guitars are usually are referred to as Selmer/Maccaferri guitars (or Selmacs for short these days).
Later when Maccaferri parted ways with the Selmer company they continued to manufacture a variation of the design with the oval hole (petite-bouche) and this version is probably the only one that could properly be referred to simply as a 'Selmer'.
All of this is from a hazy memory late at night here so pardon any errors, however the complete detailed history of the guitar is very well documented in a beautiful book by Francois Charles, entitled "The story of Selmer Maccaferri guitars".
http://www.rfcharle.com/HTML/LivreSelmerangl.html. This the definitive work on the subject and highly recommended if you have even a passing interest in the guitars (and a bit of spare cash) My copy is currently in a room with a sleeping baby so I can't check the above facts for you right now

However there are some Selmer experts on this forum (Nick, Mike, others?) who will surely correct any mistakes.